The present invention relates to irrigation and pertains particularly to a method and apparatus for sub-surface irrigation of plants.
The provision of adequate supply of moisture to growing plants has been a problem of mankind since the beginning of time. Numerous irrigation methods and techniques have been developed over the centuries. Among the most prevalent techniques are flood irrigation, sprinkler irrigation, and drip irrigation. Flood irrigation and sprinkler irrigation are utilized where water supplies are plentiful. Drip irrigation and sub-surface irrigation methods are utilized where water is scarce.
The supplying of only sufficient moisture for adequate growth of the plant directly to the roots of the plant is a technique which has been recently developed in view of the overwhelming demands on limited water supplies. Such techniques avoid the loss of large amounts of water by evaporation, run-off into adjacent areas and absorption into adjacent soil.
Among the prior art approaches to sub-surface irrigation are those illustrated in or disclosed, for example, in U.S. Pat. No. 3,443,385 issued May 13, 1969 to Voemer; U.S. Pat. No. 3,183,674 issued May 18, 1965 to Boschen; U.S. Pat. No. 1,343,871 issued June 15, 1920 to Lewis; and Italian Pat. No. 368074 issued in 1939.
The moisture control apparatus such as disclosed in the above mentioned Vollmer patent has come into widespread use in recent years because of its normally trouble free operation and conservation of water. This irrigation control system however has some minor drawbacks discovered only after extensive use. One of such drawbacks is the discovery that the system will fail to function in certain soil conditions. It is believed after extensive investigation, that this failure to function is due to a vapor lock within the moisture control unit.
Another drawback to the use of the system as disclosed in the above patent is that tree roots tend to extend to an available source of water. This results in tree roots extending into and entangling the mechanism of the moisture supply unit. Such tree roots tend to accumulate within the unit and prevent its normal operation.
Accordingly, it is desirable that a system be devised which overcomes these problems of the prior art.